[x, y] = meshgrid(-1:1.1, -2:1.2);
z = 0.5457 * exp(-0.75*y.^2 - 3.75*x.^2 - 1.5*x) .* (x + y > 1) + ...
    0.7575 * exp(-y.^2 - 6*x.^2) .* ((x + y > -1) & (x + y <= 1)) + ...
    0.5457 * exp(-0.75*y.^2 - 3.75*x.^2 + 1.5*x) .* (x + y <= -1);
contour(x, y, z);
figure;
[C, h] = contour(x, y, z);
clabel(C, h)
contourf(x, y, z);
figure;
contour3(x, y, z, 30)